Have you called your ISP? Ask them to check things on their end. May have just been some temporary outage. See if neighbors still have service.
Check all of your own incoming connections and cables. Maybe something has come loose or been unplugged. See if there are any signs of damage, corrosion, rodent chews, etc. on your service lines. Likewise for the connections and cables inside your dwelling.
Who manages the router? If the router has error logging and if the logging function is enabled you maybe able to find a clue or error within the router's logs.